/*
 * Copyright (C) 2010 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;
import com.google.common.base.Preconditions;
import java.util.Random;

/**
 * Tests the speed of iteration of different iteration methods for collections.
 *
 * @author David Richter
 */
public class MultisetIteratorBenchmark {
    @Param({"0", "1", "16", "256", "4096", "65536"})
    int size;

    LinkedHashMultiset<Object> linkedHashMultiset;
    HashMultiset<Object> hashMultiset;

    // TreeMultiset requires a Comparable element.
    TreeMultiset<Integer> treeMultiset;

    @BeforeExperiment
    void setUp() {
        hashMultiset = HashMultiset.create(size);
        linkedHashMultiset = LinkedHashMultiset.create(size);
        treeMultiset = TreeMultiset.create();

        Random random = new Random();

        int sizeRemaining = size;

        // TODO(kevinb): generate better test contents for multisets
        for (int i = 0; sizeRemaining > 0; i++) {
            // The JVM will return interned values for small ints.
            Integer value = random.nextInt(1000) + 128;
            int count = Math.min(random.nextInt(10) + 1, sizeRemaining);
            sizeRemaining -= count;
            hashMultiset.add(value, count);
            linkedHashMultiset.add(value, count);
            treeMultiset.add(value, count);
        }

        // TODO(kevinb): convert to assert once benchmark tests enable asserts by default
        Preconditions.checkState(hashMultiset.size() == size);
    }

    @Benchmark
    int hashMultiset(int reps) {
        int sum = 0;
        for (int i = 0; i < reps; i++) {
            for (Object value : hashMultiset) {
                sum += value.hashCode();
            }
        }
        return sum;
    }

    @Benchmark
    int linkedHashMultiset(int reps) {
        int sum = 0;
        for (int i = 0; i < reps; i++) {
            for (Object value : linkedHashMultiset) {
                sum += value.hashCode();
            }
        }
        return sum;
    }

    @Benchmark
    int treeMultiset(int reps) {
        int sum = 0;
        for (int i = 0; i < reps; i++) {
            for (Object value : treeMultiset) {
                sum += value.hashCode();
            }
        }
        return sum;
    }
}
